JP2019197756A - Manufacturing method for chip - Google Patents

Abstract

To easily divide a wafer while preventing damage to a device without adding optical components, such as a polarizer and multi-refractive lens, to an existing laser processor.SOLUTION: A manufacturing method for a chip comprises a first laser beam emission step in which a first modified layer is formed in only an outer peripheral surplus region of a wafer by emitting a laser beam from a rear surface side of the wafer such that focal point of the laser beam having a wavelength transmissive through the wafer is aligned with the position of a first depth in the wafer from the surface; a second laser beam emission step in which a second modified layer is then formed along a dividing line by emitting a laser beam from the rear surface side of the wafer such that the focal point of the laser beam is aligned with a position of a second depth in the wafer and further away from the surface than the position of the first depth; and a division step in which, after the first and second laser beam emission steps, external force is applied to the wafer and the wafer is divided into a plurality of chips.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a chip manufacturing method for manufacturing a plurality of chips from a wafer by dividing the wafer after irradiating the wafer with a laser beam.

  In electronic devices such as mobile phones and personal computers, device chips (hereinafter referred to as chips) such as IC (Integrated Circuit) and LSI (large-scale integrated circuit) are mounted. In this chip, for example, the surface of a wafer formed of a semiconductor material such as silicon is partitioned by a plurality of intersecting division lines (streets), devices are formed in each region, and then the wafer is formed along the division lines. It is manufactured by dividing.

  As a method of dividing the wafer, a laser beam having a wavelength that is transparent to the wafer is irradiated from the back side of the wafer and the focal point of the wafer is positioned inside the wafer, so that the wafer is divided along the planned dividing line. A processing method for forming a modified layer is known. Inside the wafer, cracks extend starting from this modified layer.

  After forming the modified layer on the wafer, the backside of the wafer is ground to reduce the thickness of the wafer, and the processing method for dividing the wafer along the planned dividing line starting from the modified layer is an SDBG (Stealth Dicing). It is called “Before Grinding” (see, for example, Patent Document 1).

  The wafer is divided into individual chips starting from the modified layer with reduced strength, but if the crack does not extend from the modified layer to the surface of the wafer where the device is formed, the wafer will be divided It may not be divided along the line. In this case, the divided chips are chipped, oblique cracks, etc. occur.

  In order to suppress chipping, oblique cracking, etc., a modified layer is formed at a depth in the wafer as close as possible to the surface of the wafer on which the device is formed, and cracks from the modified layer toward the wafer surface occur. It is effective to stretch. However, if the focal point of the laser beam is too close to the wafer surface to bring the modified layer closer to the wafer surface, the device may be damaged by the scattered light of the laser beam.

  On the other hand, to avoid damage to the device, if the laser beam output is reduced or the focal point of the laser beam is moved closer to the back surface of the wafer, cracks extend from the modified layer to the wafer surface. It becomes difficult and the wafer is not properly divided.

  By the way, the laser beam is separated into first linearly polarized light in which the vibration direction of the electromagnetic field is orthogonal to the processing progress direction and second linearly polarized light parallel to the processing progress direction, and the first linearly polarized light is collected. A technique is known in which the light spot depth position is provided on the back side of the condensing point depth position of the second linearly polarized light (see, for example, Patent Document 2).

  Since the energy density of the condensing point is higher in the first linearly polarized light than in the second linearly polarized light, the modified layer formed by the first linearly polarized light is more damaged inside the wafer. Become. As a result, a modified layer with relatively large damage to the inside of the wafer is formed on the back surface side of the wafer while suppressing damage to the device formed on the front surface side of the wafer.

JP 2014-7257 A JP 2012-16722 A

  However, in this case, an optical component such as a polarizing plate for changing the ratio of the first and second linearly polarized light and a birefringent lens for separating the laser beam into the first and second linearly polarized light is used as an existing laser. It is necessary to add to the processing equipment. The focal point depth position of the second linearly polarized light is provided on the surface side of the focal point depth position of the first linearly polarized light, and the second linearly polarized light is a region on the device inside the wafer. , The device may be damaged by the second linearly polarized scattered light.

  The present invention has been made in view of such problems, and without adding optical components such as a polarizing plate and a birefringent lens to the existing laser processing apparatus, while preventing damage to the device from the laser beam, And it aims at making it easy to divide a wafer.

  According to the present invention, a wafer having a device region including a device provided in each of a plurality of regions divided by a plurality of division lines and an outer peripheral surplus region surrounding the device region on the surface is divided. A chip manufacturing method for manufacturing a plurality of chips by dividing the wafer along a surface of the wafer, wherein a protective member is disposed on the surface side of the wafer, and the protective member side of the wafer is disposed after the placing step. A holding step of holding the chuck table, and after the holding step, a focusing point of a laser beam having a wavelength transmissive to the wafer is adjusted to a position at a first depth from the surface inside the wafer. The laser beam is irradiated from the back side of the wafer, and the first modified layer is applied only to the outer peripheral area of the wafer on the extended line of the division line. A first laser beam irradiation step to be formed; and a second depth inside the wafer that is farther from the surface than the first depth position when the focal point of the laser beam is formed after the first laser beam irradiation step. A second laser beam irradiation step of irradiating the laser beam from the back side of the wafer so as to match the position of the wafer and forming a second modified layer along the division line, and the first laser beam irradiation. After the step and the second laser beam irradiation step, there is provided a chip manufacturing method including an dividing step of applying an external force to the wafer and dividing the wafer into a plurality of chips along the planned dividing line.

  According to one aspect of the present invention, in the dividing step, the wafer is ground to a predetermined thickness by grinding means from the back side of the wafer, and the first modification is performed by grinding the wafer. The wafer is divided along the planned dividing line, starting from the quality layer and the second modified layer.

  According to the chip manufacturing method of the present invention, a crack is extended from the first and second modifications toward the surface of the wafer by being guided by the first modified layer provided in the outer peripheral surplus area where no device is formed. Therefore, the wafer is easily divided. Furthermore, since the second modified layer is provided in the device region or the like on the back surface side of the wafer from the first modified layer, compared with the case where the second modified layer is provided at the same depth position as the first modified layer. , Can reduce the damage to the device.

It is a flowchart which shows the manufacturing method of the chip | tip concerning 1st Embodiment of this invention. It is a top view of a wafer before being divided into chips. It is a figure which shows arrangement | positioning step S10 which arrange | positions a protection member. It is a figure which shows holding | maintenance step S20 which hold | maintains the surface (protection member) side of a wafer with a chuck table. It is a figure which shows 1st laser beam irradiation step S30 which forms a 1st modified layer area | region only in a peripheral surplus area | region. FIG. 6A is a diagram illustrating an example of the order of irradiating a laser beam to the outer peripheral surplus region, and FIG. 6B illustrates another example of the order of irradiating the outer peripheral surplus region with a laser beam. FIG. It is a figure which shows 2nd laser beam irradiation step S40 which forms a 2nd modified layer area | region. It is a figure which shows the surface of the wafer after S40. It is AA sectional drawing of the wafer after S40. It is a figure which shows division | segmentation step S50 which divides | segments a wafer. FIG. 11A is a view showing a state in which the wafer unit after the division step S50 is placed on the tape expansion device, and FIG. 11B is a state in which the interval between the chips 19a is widened using the tape expansion device. FIG. It is a figure which shows the some chip | tip divided | segmented from the wafer. FIG. 13A is a cross-sectional view taken along line AA of the first modified example in which the first modified layer region and the second modified layer region partially overlap in the outer peripheral surplus region, and FIG. It is AA sectional drawing of the 2nd modification in which the edge part by the side of the device area | region of 1 modification layer area | region and the edge part by the side of the outer periphery surplus area | region of 2nd modification layer area | region correspond. It is a figure which shows the device area | region and outer periphery surplus area | region which concern on 2nd Embodiment.

  FIG. 1 is a flowchart showing a manufacturing method of the chip 19a according to the first embodiment of the present invention. 2 is a top view of the wafer 11 before being divided into chips 19a, and each step shown in FIG. 1 will be described with reference to FIGS.

  In the first embodiment, after forming a modified layer by irradiating the wafer 11 with a laser beam, a plurality of chips 19 a are manufactured from the wafer 11 by the SDBG processing method in which the wafer 11 is divided by grinding the wafer 11. To do.

  As shown in FIG. 2, the wafer 11 is a disc-shaped wafer made of a semiconductor material such as silicon. The surface 11a side of the wafer 11 is divided into a plurality of regions by a plurality of division lines (streets) 17 intersecting each other, and a device 19 such as an IC is formed in each region.

  The material, shape, structure, size, etc. of the wafer 11 are not limited. For example, a substrate made of a material other than silicon, such as a semiconductor, ceramics, resin, metal, or the like can be used as the wafer 11. Similarly, the type, quantity, shape, structure, size, arrangement, etc. of the device 19 are not limited.

  The wafer 11 includes a device region 13 including a plurality of devices 19 and an outer peripheral surplus region 15 surrounding the device region 13 and not provided with the device 19. The outer peripheral surplus region 15 of the present embodiment is an annular region, the inner end of the annular region is adjacent to the corners of the plurality of devices 19, and the outer end of the annular region is the crystal of the wafer 11. It has a notch 15a indicating the orientation.

  In FIG. 2, the boundary between the device region 13 and the outer peripheral surplus region 15 in the present embodiment is indicated by a broken line. The boundary is circular, and the device region 13 is inside the boundary. Note that the device region 13 of the present embodiment includes a region adjacent to the device 19 where the device 19 is not formed.

  In FIG. 2, an extension line 17 a extending from the planned division line 17 of the device region 13 is indicated by a broken line. The extension line 17 a of the present embodiment is located in the device region 13 and the outer peripheral surplus region 15.

  As described above, the device 19 is formed on the surface 11 a side of the wafer 11. Therefore, in order to protect the device 19 in the processing process of the wafer 11, a disk-shaped resin protective member 21 having the same diameter as the wafer 11 is disposed on the surface 11a side of the wafer 11 (arrangement step S10). .

  FIG. 3 is a diagram illustrating an arrangement step S10 in which the protection member 21 is arranged. In FIG. 3, the extension line 17a of the division planned line 17 is omitted. After the placement step S <b> 10, a modified layer is formed on the wafer 11 using the laser processing apparatus 12.

  For this purpose, first, the protective member 21 side of the wafer 11 is disposed on the upper surface of the chuck table 20 of the laser processing apparatus 12. FIG. 4 is a diagram illustrating a holding step S <b> 20 in which the surface 11 a (protective member 21) side of the wafer 11 is held by the chuck table 20.

  The chuck table 20 has a circular upper surface larger than the wafer 11, and the upper surface is formed substantially parallel to the X-axis direction and the Y-axis direction. A moving mechanism (not shown) is provided below the chuck table 20, and the chuck table 20 can be moved in the horizontal direction (XY plane direction) by the moving mechanism.

  Note that the X-axis direction, the Y-axis direction, and the Z-axis direction used in the description of the present specification are perpendicular to each other. In addition, it should be noted that “upper”, “lower”, and the like are merely convenient expressions for specifying the position of the component, and do not necessarily indicate a direction parallel to the direction of gravity.

  The central region of the upper surface of the chuck table 20 is a holding surface 20a formed of porous ceramics or the like, and the holding surface 20a is vacuumed via a suction path (not shown) formed inside the chuck table 20. It is connected to suction means (not shown) such as a pump. Due to the negative pressure of the suction means, the wafer 11 placed on the holding surface 20a is sucked and held on the chuck table 20 (holding step S20).

  After the holding step S <b> 20, only the outer peripheral surplus area 15 of the wafer 11 is irradiated with a laser beam having a predetermined wavelength that is transmissive to the wafer 11. The predetermined wavelength is, for example, about 1064 nm or about 1300 nm.

  The laser processing apparatus 12 (see FIG. 5) that emits a laser beam has a laser irradiation unit 14, and the laser irradiation unit 14 includes a laser processing head 16 that emits a pulsed laser beam from the tip. The laser processing head 16 has a lens for condensing the emitted laser beam therein.

  Further, the laser processing apparatus 12 includes an imaging unit 18 that is branched from the main body of the laser irradiation unit 14 and is disposed in the vicinity of the laser processing head 16. The image of the wafer 11 picked up by the image pickup unit 18 is used for alignment between the wafer 11 and the laser processing head 16.

  FIG. 5 is a diagram showing a first laser beam irradiation step S <b> 30 in which the first modified layer region is formed only in the outer peripheral surplus region 15 using the laser processing apparatus 12. The laser beam applied to the wafer 11 is condensed at a specific depth position inside the wafer 11. Multi-photon absorption occurs at this condensing point, and the mechanical strength and the like are reduced by changing the quality of the wafer 11.

  The laser beam is irradiated along the relative movement path while relatively moving the laser processing head 16 and the chuck table 20. In the first laser beam irradiation step S30 of the present embodiment, only the outer peripheral surplus area 15 on the extension line 17a of the division planned line 17 in the device area 13 is irradiated from the back surface 11b side of the wafer 11.

  Thereby, the modified layer can be formed only in the outer peripheral surplus region 15. The modified layer is, for example, a region where a crack is generated in the wafer 11 or a region where the wafer 11 is partially melted.

  In the first laser beam irradiation step S30, the depth position of the laser beam condensing point is adjusted so that three modified layers 25a, 25b, and 25c are formed at different depth positions from the surface 11a inside the wafer 11. . Thus, the first modified layer region 25 including the three modified layers 25a, 25b, and 25c is formed (see FIG. 9).

  Since the depth position of the condensing point can be adjusted by moving the position of the lens in the laser processing head 16 up and down, in the first modified layer region 25, the modified layer 25a is formed at a position closest to the surface 11a, The modified layer 25c is formed at a position closest to the back surface 11b, and the modified layer 25b is formed between the modified layer 25a and the modified layer 25c.

  The intervals between the modified layers 25a, 25b, and 25c can be adjusted as appropriate according to the thickness of the wafer 11. For example, when the thickness of the wafer 11 is 740 μm, the distance between the modified layer 25a and the modified layer 25b in the thickness direction of the wafer 11 and the distance between the modified layer 25b and the modified layer 25c are each 50 μm or more. 70 μm or less. However, the interval between the modified layers is not limited to this range.

  When the three modified layers 25a, 25b, and 25c are formed, the relative movement speeds of the laser processing head 16 and the chuck table 20 that holds the wafer 11 are the same. However, the output of the laser beam may be changed according to the depth position of the condensing point. For example, the laser beam output at the time of formation is reduced as the modified layer is closer to the surface 11a.

  In the present embodiment, the laser beam output when forming the first modified layer region 25 is the smallest when the modified layer 25a closest to the front surface 11a is formed, and when the modified layer 25c closest to the back surface 11b is formed. Is the largest. Thereby, the influence which the scattered light to the surface 11a of a laser beam has on the device 19 can be reduced compared with the case where the output at the time of formation of the modified layer 25a and the modified layer 25c is the same.

  Here, an example of the order of laser beam irradiation in the first laser beam irradiation step S30 will be described with reference to FIG. In the example of FIG. 6A, first, a laser beam is irradiated along the extended line 17a of the outer peripheral surplus region 15 passing through the notch 15a.

  Next, the output of the laser beam is temporarily turned off, and the laser processing head 16 is positioned on the left line 17b1 of the extension line 17a of the outer peripheral surplus region 15 closest to the notch 15a. Then, the output of the laser beam is turned on again, and the laser beam is irradiated along the line 17b1.

  Thereafter, the output of the laser beam is temporarily turned off, and the laser processing head 16 is positioned on the right line 17c1 of the extension line 17a of the outer peripheral surplus region 15 closest to the notch 15a. Then, the output of the laser beam is turned on again, and the laser beam is irradiated along the line 17c1.

  Similarly, the laser beam is then irradiated along the line 17b2 on the extension line 17a of the outer peripheral surplus region 15 adjacent to the left side of the line 17b1. Then, a laser beam is irradiated along the line 17c2 on the extension line 17a of the outer periphery surplus area | region 15 adjacent to the right side of the line 17c1. In this manner, laser beam irradiation is advanced alternately left and right in the order of proximity to the notch 15a.

  When a plurality of modified layers are provided at different positions in the thickness direction of the wafer 11, a laser beam condensing point is set at a predetermined depth position, and the laser beam is alternately left and right as described above. Proceed with irradiation. Then, after changing the depth position of the condensing point of the laser beam, the laser beam irradiation is advanced alternately left and right as described above.

  Instead of the example of FIG. 6 (A), as shown in FIG. 6 (B), starting from the irradiation of the laser beam along the extension line 17a of the outer peripheral surplus region 15 passing through the notch 15a, the line 17b1, Irradiation may proceed clockwise in the order of the line 17b2 and the line 17b3 on the extension line 17a of the outer peripheral surplus region 15 adjacent to the left side of the line 17b2. Note that FIGS. 6A and 6B are examples of the order of irradiation, and the order of irradiation is not limited thereto.

  After the first laser beam irradiation step S30, the laser beam is irradiated onto the division line 17 in the device region 13 and the extension line 17a of the division line 17 in the device region 13 and the outer peripheral surplus region 15. Thereby, the second modified layer region is formed. FIG. 7 is a diagram showing a second laser beam irradiation step S40 for forming the second modified layer region.

  In the second laser beam irradiation step S40, the laser beam is irradiated not only on the device region 13 but also on the outer peripheral surplus region 15. Further, the laser beam is focused from the back surface 11b side of the wafer 11 so that the focal point of the laser beam is adjusted to a depth position farther from the front surface 11a than the depth position of each modified layer in the first modified layer region 25. Irradiate.

  The second modified layer region 27 formed on the back surface 11b side with respect to the first modified layer region 25 includes three modified layers 27a, 27b, and 27c formed at different depth positions from the front surface 11a (see FIG. 9).

  In the second modified layer region 27, the modified layer 27a is formed at a position closest to the front surface 11a, the modified layer 27c is formed at a position closest to the back surface 11b, and the modified layer 27b is modified with the modified layer 27a. It is formed between the material layer 27c.

  The intervals between the three modified layers 27a, 27b, and 27c can be changed as appropriate according to the thickness of the wafer 11. For example, when the thickness of the wafer 11 is 740 μm, the distance between the modified layer 27 a and the modified layer 27 b in the thickness direction of the wafer 11 and the distance between the modified layer 27 b and the modified layer 27 c are 50 μm or more and 70 μm, respectively. It is as follows. However, the interval between the modified layers is not limited to this range.

  When the three modified layers 27a, 27b, and 27c are formed, the relative moving speed and the like of the laser processing head 16 and the chuck table 20 that holds the wafer 11 are the same. However, the output of the laser beam may be changed according to the depth position of the condensing point. For example, the laser beam output at the time of formation is reduced as the modified layer is closer to the surface 11a.

  In the present embodiment, the output of the laser beam when forming the second modified layer region 27 is smallest when the modified layer 27a closest to the front surface 11a is formed, and when the modified layer 27c closest to the back surface 11b is formed. Is the largest. Thereby, the influence which the scattered light to the surface 11a of a laser beam has on the device 19 can be reduced compared with the case where the output at the time of formation of the modified layer 27a and the modified layer 27c is the same.

  In addition, the modified layer 27 a located closest to the front surface 11 a in the second modified layer region 27 and the modified layer 25 c located closest to the back surface 11 b in the first modified layer region 25 of the wafer 11. The interval in the thickness direction may be determined as appropriate, but is, for example, about 100 μm.

  FIG. 8 shows the surface 11a of the wafer 11 after the second laser beam irradiation step S40, and FIG. 9 shows a cross-sectional view taken along the line AA of FIG. In FIG. 8, the range in which the first modified layer region 25 and the second modified layer region 27 are provided is indicated by a solid line. Further, in FIG. 9, the modified layers 27a, 27b, and 27c orthogonal to the modified layers 27a, 27b, and 27c crossing the wafer 11 are indicated by dots.

  As described above, in the present embodiment, the first modified layer region 25 is provided only in the outer peripheral surplus region 15 having a depth range relatively close to the surface 11a. Therefore, compared with the case where the first modified layer region 25 and the second modified layer region 27 are provided in the same depth range, the influence of the scattered light of the laser beam toward the surface 11a side of the wafer 11 can be reduced, Damage to the device 19 can be prevented.

  In addition, the cracks formed in the second modified layer region 27 are likely to reach the surface 11a side by being induced by cracks extending in the horizontal direction and the vertical direction of the wafer 11 from the first modified layer region 25. Thereby, the wafer 11 is easily divided. Note that cracks also extend from the first modified layer region 25 and the second modified layer region 27 to the back surface 11b side.

  In the present embodiment, since the laser beam is not separated into two linearly polarized light, it is not necessary to add optical components such as a polarizing plate and a birefringent lens to the existing laser processing apparatus 12. In this manner, the wafer 11 can be easily divided while preventing damage to the device 19 from the laser beam.

  After the first laser beam irradiation step S30 and the second laser beam irradiation step S40, a dividing step S50 for dividing the wafer 11 is executed. In the present embodiment, as shown in FIG. 10, the wafer 11 is divided by a grinding device (grinding means) 28.

  The grinding device 28 includes a chuck table 40 that sucks and holds the wafer 11. The chuck table 40 sucks and holds the protective member 21 side (that is, the surface 11a side) of the wafer 11 disposed on the holding surface 40a by suction means (not shown). The chuck table 40 is connected to a rotation drive source (not shown) such as a motor, and rotates around the rotation axis of the rotation drive source.

  Above the chuck table 40, the grinding wheel 30 is disposed so as to face the holding surface 40a. A plurality of grinding wheels 38 are annularly fixed to the lower surface of the wheel base 36 of the grinding wheel 30.

  The upper surface of the wheel base 36 is fixed to the wheel mount 34, and when the spindle 32 connected to the wheel mount 34 rotates, the grinding wheel 38 also rotates around the rotation axis of the spindle 32.

  By rotating the grinding wheel 30 and the chuck table 40 relative to each other, the grinding wheel 30 is lowered and the grinding wheel 38 is pressed against the wafer 11, whereby the wafer 11 is ground from the back surface 11 b side and has a predetermined thickness (finishing). Thickness).

  In addition, since the external force such as pressure is applied to the wafer 11 from the grinding wheel 30 by the operation of grinding the wafer 11, the first modified layer region 25 and the second modified layer region 27 having reduced strength are formed. Cracks can further extend at the starting point.

  When the wafer 11 is ground to a thickness range where cracks exist, the wafer 11 is divided into a plurality of chips 19a. In this manner, the wafer 11 is divided along the scheduled division line 17 starting from the first modified layer region 25 and the second modified layer region 27, and a plurality of chips 19a are manufactured (see FIG. 12).

  In the present embodiment, the chip 19a is manufactured by grinding the wafer 11 to such a thickness that the first modified layer region 25 and the second modified layer region 27 do not remain. However, at least one modified layer may be intentionally left on the manufactured chip 19a. Whether to leave the modified layer on the chip 19a may be determined according to product specifications.

  The wafer 11 is difficult to be divided when the so-called finish thickness left after grinding is relatively large, or when a relatively thick metal layer is provided in contact with the surface 11a. In such a case, it is particularly effective to provide the first modified layer region 25 and the second modified layer region 27 of the present embodiment on the wafer 11.

  In the first modified layer region 25 of the present embodiment, three modified layers 25a, 25b, and 25c are formed at different depth positions of the wafer 11, but the modified layers included in the first modified layer region 25 are formed. There is no limit to the number of strata. In the first modified layer region 25, at least one modified layer of the three modified layers 25a, 25b, and 25c may be formed.

  Similarly, the number of the modified layers included in the second modified layer region 27 is not limited, and the second modified layer region 27 includes at least one modified layer among the three modified layers 27a, 27b, and 27c. A layer may be formed. Also in this case, it can be expected that cracks extend in the front surface 11a side, the back surface 11b side, and the horizontal direction of the wafer 11.

  Note that, as another alternative means of dividing step S50 in which an external force is applied to the wafer 11 to divide the wafer 11 into a plurality of chips 19a, the dividing step S50 may be executed by applying an external force by a braking device.

  Next, an experimental example in which the effect of this embodiment has been confirmed will be described. In Experimental Example 1 in which the first modified layer region 25 and the second modified layer region 27 are provided and in Comparative Example 1 in which only the second modified layer region 27 is provided, the thickness after grinding and the surface of the wafer 11 The presence or absence of cracks in 11a was compared. In Experimental Example 1 and Comparative Example 1, the device 19 was not formed on the surface 11a, but each modified layer was formed along the planned dividing line 17 set according to the position of the device 19.

  (Experiment 1) In Experiment 1, the wafer 11 having a thickness of 742 μm is irradiated with a laser beam from the rear surface 11b, and the modified layer 27a closest to the surface 11a in the second modified layer region 27 is changed to the surface 11a. A plurality of samples with different distances in the depth direction were prepared.

  In each sample of Experimental Example 1, the first modified layer region 25 was also formed between the second modified layer region 27 and the surface 11a. Then, when the surface 11a of the wafer 11 was observed, it was determined whether or not a crack along the planned dividing line 17 was observed.

  When the distance from the modified layer 27a to the surface 11a was about 100 μm and 200 μm, cracks along the planned division line 17 were observed on the surface 11a in all samples. However, when the distance is 326 μm (that is, about 44% of the wafer 11 (= (326 μm / 742 μm) × 100)) or more, there are samples in which cracks are observed on the surface 11a and samples in which no cracks are observed. It was. The distance between the modified layer 27a and the modified layer 25c was about 140 μm.

  (Comparative Example 1) In Comparative Example 1, the wafer 11 having a thickness of 742 μm is irradiated with a laser beam from the back surface 11b, and from the modified layer 27a closest to the surface 11a in the second modified layer region 27 to the surface 11a. A plurality of samples with different distances in the depth direction were prepared. Then, when the surface 11a of the wafer 11 was observed, it was determined whether or not a crack along the planned dividing line 17 was observed.

  When the distance from the modified layer 25a to the surface 11a was about several tens of μm, cracks along the planned dividing line 17 were observed on the surface 11a in all samples. However, when the distance is 106 μm (that is, about 14% of the wafer 11 (= (106 μm / 742 μm) × 100)) or more, there are samples in which cracks are observed on the surface 11a and samples in which no cracks are observed. It was.

  Thus, in Experimental Example 1, even if the distance between the modified layer 27a and the surface 11a is about three times the distance between the modified layer 27a and the surface 11a in Comparative Example 1, cracks along the planned dividing line 17 occur. Was observed on the surface 11a. That is, the effectiveness of providing the first modified layer region 25 in order to extend the crack to the surface 11a was confirmed.

  Next, in order to pick up the manufactured chip 19a, an interval expansion step for increasing the interval between the chips 19a will be described. The interval expansion step may be executed after the division step S50. In the following, a case where a DAF (Die Attach Film) 11d is provided as an adhesive layer for mounting the manufactured chip 19a will be described, but the DAF 11d may be omitted.

  FIG. 11A is a diagram showing a state where the wafer unit after the division step S50 is placed on the tape expansion device 50, and FIG. 11B is a diagram in which the tape expansion device 50 is used to widen the interval between the chips 19a. FIG.

  A DAF 11d having an area larger than that of the wafer 11 is attached to the back surface 11b of the wafer 11, and an expanded tape 11e having an area larger than that of the DAF 11d is attached to the opposite side of the DAF 11d from the wafer 11. Yes. The DAF 11d and the expanded tape 11e are used in place of the above-described protective member 21 when increasing the distance between the chips 19a.

  On the surface of the expanded tape 11e on the side where the DAF 11d is provided, a metal annular frame 11c having an opening larger in area than the wafer 11 is attached. The wafer 11, the DAF 11d, the expanded tape 11e, and the annular frame 11c constitute a wafer unit.

  As shown in FIG. 11A, the wafer 11 of the wafer unit is arranged on the chuck table 60 of the tape expansion device 50. The chuck table 60 is provided at the top end of the support leg 54 that supports the chuck table 60.

  The chuck table 60 includes a frame portion 60b formed from a metal such as stainless steel, and a suction holding portion 60c configured from a porous member such as porous ceramics disposed in a recess of the frame portion 60b. The suction holding unit 60c is provided so as to be exposed on the surface of the chuck table 60 opposite to the support leg 54, and sucks and holds the wafer 11 via the DAF 11d and the expanding tape 11e.

  A frame holding table 52 for supporting the annular frame 11c of the wafer unit and a plate 56 for pressing the annular frame 11c from above are provided at positions surrounding the chuck table 60 and the support legs 54.

  When the moving means (not shown) is operated to press the plate 56 downward, the annular frame 11 c pressed by the plate 56 is fixed to the frame holding table 52. The annular frame 11 c is held by the frame holding table 52 and the plate 56.

  Next, an elevating mechanism (not shown) is operated to move the piston rod 58 downward as shown in FIG. 11B, and the frame holding table 52 and the annular frame 11c fixed by the plate 56 are connected to the chuck table. Pull against 60. That is, the holding surface 60a of the chuck table 60 is pushed up with respect to the annular frame 11c.

  Thereby, the expanded tape 11e is expanded in the radial direction, and as a result, the interval between the individual chips 19a is widened. Note that the DAF 11d attached to the back surface 11b of the chip 19a is also separated into individual pieces along with the division of the chip 19a, and the interval between the pieces is also expanded corresponding to the chip 19a.

  Thereafter, the expanded tape 11e expanded through the suction holding portion 60c is sucked and held by a suction means (not shown). Thereby, since the interval between the individual chips 19a adjacent to each other after the division is maintained expanded, the pickup of each chip 19a is facilitated. FIG. 12 is a diagram showing a plurality of chips 19 a divided from the wafer 11.

  Next, a modified example in which the range in which the second modified layer region 27 is formed will be described. FIG. 13A is a cross-sectional view taken along line AA of the first modification in which the first modified layer region 25 and the second modified layer region 27 partially overlap in the outer peripheral surplus region 15.

  In the second laser beam irradiation step S40 of the first modified example, the laser beam is irradiated along the extension line 17a of the division planned line 17 from the outer peripheral end of the device region 13 to a position before the outer peripheral end of the wafer 11. .

  That is, in 2nd laser beam irradiation step S40 of a 1st modification, in addition to the division | segmentation scheduled line 17 of the device area | region 13, and its extension line 17a, a part of inner peripheral edge part vicinity of the extension line 17a of the outer periphery surplus area | region 15 Irradiate the laser beam.

  As a result, the first modified layer region 25 and the second modified layer region 27 have a length L from the outer peripheral end of the device region 13 to the front of the outer peripheral end of the wafer 11 when viewed from the front surface 11a or the back surface 11b. Only overlap. Also in the first modification, the same advantageous effects as in the first embodiment can be obtained.

  FIG. 13B shows an A- of the second modified example in which the end portion on the device region 13 side of the first modified layer region 25 and the end portion on the outer peripheral surplus region 15 side of the second modified layer region 27 coincide. It is A sectional drawing. In the second laser beam irradiation step S40 of the second modification, only the device region 13 is irradiated with a laser beam without irradiating the outer peripheral surplus region 15 with the laser beam. Also in the second modified example, the same advantageous effects as in the first embodiment can be obtained.

  As described above, the end portion of the second modified layer region 27 on the outer peripheral surplus region 15 side may be located at the outer peripheral end portion of the wafer 11 as shown in (i) FIG. 9, and (ii) FIG. ), It may be located between the outer peripheral end of the wafer 11 and the end of the first modified layer region 25 on the device region 13 side.

  Further, the end portion of the second modified layer region 27 on the outer peripheral surplus region 15 side is in the planar direction of the wafer 11 (iii) as shown in FIG. 13B, the device region 13 of the first modified layer region 25. It may coincide with the end on the side. One wafer 11 may include two or more types (i) to (iii).

  FIG. 14 is a diagram illustrating the device region 13 and the outer peripheral surplus region 15 according to the second embodiment. The boundary between the device region 13 and the outer peripheral surplus region 15 is indicated by a broken line. The device region 13 of the second embodiment has a shape along the outer periphery of the plurality of devices 19.

  That is, the device region 13 of the second embodiment is a region that includes a plurality of devices 19 and division lines 17 but does not include the extension line 17a when the wafer 11 is viewed from the front surface 11a side. On the other hand, the outer peripheral surplus area 15 is an area that includes the extension line 17 a but does not include the plurality of devices 19 and the planned division lines 17.

  Also in the second embodiment, in the first laser beam irradiation step S <b> 30, only the outer peripheral surplus region 15 of the wafer 11 is irradiated with the laser beam. Other steps of the manufacturing method of the chip 19a are the same as those in the first embodiment. In the second embodiment, the area of the outer peripheral surplus region 15 and the range in which the first modified layer region 25 is formed are larger than those in the first embodiment. Therefore, the crack is likely to extend on the surface 11a of the wafer 11 as compared with the first embodiment.

  The second embodiment may be combined with the first modification or the second modification of the first embodiment. Further, the second embodiment and the interval expansion step may be combined. In addition, the structure, method, and the like according to the above-described embodiment can be appropriately modified and implemented without departing from the scope of the object of the present invention.

11 Wafer 11a Front 11b Back 11c Annular frame 11d DAF
11e Expanding tape 12 Laser processing device 13 Device area 14 Laser irradiation unit 15 Peripheral surplus area 15a Notch 16 Laser processing head 17 Scheduled line (street)
17a extension line 17b1, 17b2, 17b3, 17c1, 17c2 line 18 imaging unit 19 device 19a chip 20 chuck table (holding means)
20a Holding surface 21 Protective member 25 First modified layer region 25a, 25b, 25c Modified layer 27 Second modified layer region 27a, 27b, 27c Modified layer 28 Grinding device (grinding means)
DESCRIPTION OF SYMBOLS 30 Grinding wheel 32 Spindle 34 Wheel mount 36 Wheel base 38 Grinding wheel 40 Chuck table 40a Holding surface 50 Tape expansion device 52 Frame holding table 54 Support leg 56 Plate 58 Piston rod 60 Chuck table 60a Holding surface 60b Frame part 60c Suction holding part

Claims (2)

Dividing a wafer having a device area including devices provided in each of a plurality of areas partitioned by a plurality of division lines and an outer peripheral surplus area surrounding the device area along the division lines. A chip manufacturing method for manufacturing a plurality of chips by:
An arrangement step of arranging a protective member on the surface side of the wafer;
A holding step of holding the protective member side of the wafer with a chuck table after the placing step;
After the holding step, the laser beam is placed on the back surface of the wafer so that the focal point of the laser beam having a wavelength transmissive to the wafer is aligned with a first depth from the surface inside the wafer. A first laser beam irradiation step of forming a first modified layer only on the outer peripheral surplus region of the wafer on the extension line of the division schedule line,
After the first laser beam irradiation step, the laser beam is adjusted so that the focal point of the laser beam is aligned with a second depth inside the wafer that is farther from the surface than the first depth position. A second laser beam irradiation step for forming a second modified layer along the division line,
A dividing step of applying an external force to the wafer after the first laser beam irradiation step and the second laser beam irradiation step, and dividing the wafer into a plurality of chips along the division line;
A method for manufacturing a chip, comprising: In the dividing step,
The wafer is ground from the back side of the wafer by a grinding means to be processed to a predetermined thickness, and the wafer is ground from the first modified layer and the second modified layer by the operation of grinding the wafer. The chip manufacturing method according to claim 1, wherein the chip is divided along the division line.